libstdc++
numeric_traits.h
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1 // -*- C++ -*-
2 
3 // Copyright (C) 2007, 2009 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
9 // version.
10 
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file ext/numeric_traits.h
26  * This file is a GNU extension to the Standard C++ Library.
27  */
28 
29 #ifndef _EXT_NUMERIC_TRAITS
30 #define _EXT_NUMERIC_TRAITS 1
31 
32 #pragma GCC system_header
33 
34 #include <bits/cpp_type_traits.h>
35 #include <ext/type_traits.h>
36 
37 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
38 
39  // Compile time constants for builtin types.
40  // Sadly std::numeric_limits member functions cannot be used for this.
41 #define __glibcxx_signed(_Tp) ((_Tp)(-1) < 0)
42 #define __glibcxx_digits(_Tp) \
43  (sizeof(_Tp) * __CHAR_BIT__ - __glibcxx_signed(_Tp))
44 
45 #define __glibcxx_min(_Tp) \
46  (__glibcxx_signed(_Tp) ? (_Tp)1 << __glibcxx_digits(_Tp) : (_Tp)0)
47 
48 #define __glibcxx_max(_Tp) \
49  (__glibcxx_signed(_Tp) ? \
50  (((((_Tp)1 << (__glibcxx_digits(_Tp) - 1)) - 1) << 1) + 1) : ~(_Tp)0)
51 
52  template<typename _Value>
53  struct __numeric_traits_integer
54  {
55  // Only integers for initialization of member constant.
56  static const _Value __min = __glibcxx_min(_Value);
57  static const _Value __max = __glibcxx_max(_Value);
58 
59  // NB: these two also available in std::numeric_limits as compile
60  // time constants, but <limits> is big and we avoid including it.
61  static const bool __is_signed = __glibcxx_signed(_Value);
62  static const int __digits = __glibcxx_digits(_Value);
63  };
64 
65  template<typename _Value>
66  const _Value __numeric_traits_integer<_Value>::__min;
67 
68  template<typename _Value>
69  const _Value __numeric_traits_integer<_Value>::__max;
70 
71  template<typename _Value>
72  const bool __numeric_traits_integer<_Value>::__is_signed;
73 
74  template<typename _Value>
75  const int __numeric_traits_integer<_Value>::__digits;
76 
77 #undef __glibcxx_signed
78 #undef __glibcxx_digits
79 #undef __glibcxx_min
80 #undef __glibcxx_max
81 
82 #define __glibcxx_floating(_Tp, _Fval, _Dval, _LDval) \
83  (std::__are_same<_Tp, float>::__value ? _Fval \
84  : std::__are_same<_Tp, double>::__value ? _Dval : _LDval)
85 
86 #define __glibcxx_max_digits10(_Tp) \
87  (2 + __glibcxx_floating(_Tp, __FLT_MANT_DIG__, __DBL_MANT_DIG__, \
88  __LDBL_MANT_DIG__) * 3010 / 10000)
89 
90 #define __glibcxx_digits10(_Tp) \
91  __glibcxx_floating(_Tp, __FLT_DIG__, __DBL_DIG__, __LDBL_DIG__)
92 
93 #define __glibcxx_max_exponent10(_Tp) \
94  __glibcxx_floating(_Tp, __FLT_MAX_10_EXP__, __DBL_MAX_10_EXP__, \
95  __LDBL_MAX_10_EXP__)
96 
97  template<typename _Value>
98  struct __numeric_traits_floating
99  {
100  // Only floating point types. See N1822.
101  static const int __max_digits10 = __glibcxx_max_digits10(_Value);
102 
103  // See above comment...
104  static const bool __is_signed = true;
105  static const int __digits10 = __glibcxx_digits10(_Value);
106  static const int __max_exponent10 = __glibcxx_max_exponent10(_Value);
107  };
108 
109  template<typename _Value>
110  const int __numeric_traits_floating<_Value>::__max_digits10;
111 
112  template<typename _Value>
113  const bool __numeric_traits_floating<_Value>::__is_signed;
114 
115  template<typename _Value>
116  const int __numeric_traits_floating<_Value>::__digits10;
117 
118  template<typename _Value>
119  const int __numeric_traits_floating<_Value>::__max_exponent10;
120 
121  template<typename _Value>
122  struct __numeric_traits
123  : public __conditional_type<std::__is_integer<_Value>::__value,
124  __numeric_traits_integer<_Value>,
125  __numeric_traits_floating<_Value> >::__type
126  { };
127 
128 _GLIBCXX_END_NAMESPACE
129 
130 #undef __glibcxx_floating
131 #undef __glibcxx_max_digits10
132 #undef __glibcxx_digits10
133 #undef __glibcxx_max_exponent10
134 
135 #endif
GNU extensions for public use.